1. Field of the Invention
The present invention is generally related to a steering device for a marine propulsion system and, more particularly, to an integrated steering system that is disposed within a support structure of the marine propulsion unit to minimize the movement of components of the steering actuator relative to support structure when the marine propulsion system is rotated either about its steering axis or its tilting axis.
2. Description of the Prior Art
As is well known to those skilled in the art of marine propulsion systems, As hydraulically actuated steering systems or power steering systems typically incorporate hydraulic cylinders that are mounted on the marine propulsion system in a way that requires portions of the hydraulic actuator to move with the marine propulsion system as it is tilted about its tilting axis or rotated about its steering axis. This arrangement causes interference between associated components of the marine propulsion system.
U.S. Pat. No. 5,997,370, which issued to Fetchko et al on Dec. 7, 1999, describes an outboard hydraulic steering assembly with reduced support bracket rotation. The hydraulic steering assembly applies a force to a tiller arm of a marine, outboard propulsion unit and rotates the propulsion unit about a steering axis between a center position and hard over positions to each side of the center position. The propulsion unit is supported for arcuate movement about a tilt axis which is generally perpendicular to the steering axis. The steering assembly includes a hydraulic steering cylinder with an elongated piston rod reciprocatingly mounted within the cylinder for movement along a piston rod axis. A pair of support arms are pivotable about the tilt axis and are connected to the piston rod, allowing arcuate movement of the rod about the tilt axis, while maintaining the rod axis parallel to the tilt axis. A member is pivotally mounted on the tiller arm for pivoting about a first axis which is parallel to the steering axis. The cylinder arm is connected to the cylinder and extends radially outwards from the piston rod axis. The cylinder arm is pivotally connected to the member for pivoting about the second link axis which is parallel to the piston rod axis. The cylinder arm moves through a partially rotated position when the propulsion unit rotates from the center position to either hard over position. The second link axis and the rod axes are on a plane parallel to the steering axis at the partially rotated position.
U.S. Pat. No. 4,419,084, which issued to Borst on Dec. 6, 1983, describes a power assisted steering mechanism for a marine propulsion device. An outboard motor for a boat includes a support adapted to be fixed relative to the boat hull, and a propulsion assembly including a rotatably mounted propeller. It is connected to the support for pivotal steering movement about a steering axis. The outboard motor also includes a pair of elongated members, coupled together for linear extension and retraction upon rotation of one of the elongated members with respect to the other of the elongated members, with the end of one of the members being connected to the propulsion assembly for causing pivotal movement of the propulsion assembly about the steering axis. It further comprises an assembly for fixing the other of the elongated members against longitudinal movement and a push pull cable assembly for selectively causing rotation of one of the elongated members with respect to the other of the elongated members.
U.S. Pat. No. 4,449,470, which issued to Rump on May 22, 1984, describes an hydraulic control package for a marine steering system. The package is intended for use in a marine steering system which has a steering helm pump with port and starboard fluid outlets and a return inlet for hydraulically actuating a piston in a hydraulic cylinder having port and starboard inlets for moving the piston back and forth in the cylinder in response to fluid delivered from the helm pump. A fluid reservoir is closed and pressurized with air and is defined by an open ended tube having a cap sealing the top end of the tube and a valve body sealing the bottom end of the tube. The valve body houses the control valve means for controlling the fluid flow in the system between the helm pump and the actuating cylinder. The cap and valve body are held against the respective ends of the tube by tie rods. The assembly may also include a plurality of steering pumps connected in parallel and through shuttle-tee check valves to the control valve means with a restrictive bypass extending about each shuttle-tee check valve for preventing the nonactive pump from motoring in response to steering fluid output of the active pump while allowing a limited amount of the steering fluid output to flow to the nonactive steering pump.
U.S. Pat. No. 4,773,882, which issued to Rump on Sep. 27, 1988, describes a hydraulic steering assembly for outboard engines. The assembly is secured to a tiller arm of a variety of outboard propulsion units for a boat so as to rotate a propulsion unit about a steering axis. The assembly comprises a hydraulic cylinder having a hydraulically actuated rod member extending therefrom and being rotatably secured to the tiller arm of an outboard propulsion unit about an axis of rotation parallel to the steering axis. The hydraulic cylinder also includes a pivotal connection for attachment to the boat to define a pivot axis generally parallel to the steering axis and nonrotatable about the steering axis. The force exerted by actuation of the hydraulic cylinder against the pivotal connection rotates the outboard propulsion unit about the steering axis.
U.S. Pat. No. 4,228,757, which issued to Wood on Oct. 21, 1980, describes a boat steering assembly. The assembly has a tiller lever for providing a steering input upon being pivoted about a first pivot axis and an actuating lever supported for pivotal movement about a second pivot axis. The ends of the levers are interconnected in order to pivot the tiller lever upon pivoting movement of the actuating lever and for positioning the levers in parallel relationship with one another in a neutral position. The length of the tiller lever from its first pivot is longer than the length of the actuating lever from its second pivot to their respective ends. There is also an actuator assembly comprising a reciprocating member having a hydraulically operated piston at each end which is slidably disposed for movement between two cylinders which are defined by a housing. A first end of a actuating member is operatively connected to the housing and a second end extends out of the housing and is adapted for connection to a steering means. A drive member supported by the reciprocating member provides a driving connection between the actuating lever and the reciprocating member.
U.S. Pat. No. 4,592,732, which issued to Ferguson on Jun. 3, 1986, describes a marine propulsion device power steering system. A marine propulsion device is adapted for mounting to a boat transom and comprises a propulsion unit, a swivel bracket connecting the propulsion unit to the boat transom for pivotal movement of the propulsion unit relative to the boat transom about its steering axis and an extendable and contractable steering link which is pivotally connected to the boat transom and to the propulsion unit for rotating the propulsion unit about the steering axis. The device further comprises an operator actuated extendable and contractable control link connected to the boat transom and to the propulsion unit and operably connected to the steering link for selectively effecting extension and contraction of the steering link in response to operator actuation of the control link.
U.S. Pat. No. 5,127,856, which issued to Kabuto et al on Jul. 7, 1992, describes a power steering system for an outboard motor. The system is capable of permitting an electric motor to be driven only when the driving of the electric motor is required and automatically controlling the steering force of a steering wheel depending upon the steering reaction force. The system is so constructed that a steering cable is moved depending upon the rotation of the steering wheel and the movement of the steering cable is detected by means of a steering force sensor which supplies a signal to a controller. The controller controls the output of the electric motor depending upon the signal.
U.S. Pat. No. 5,240,445, which issued to Aoki et al on Aug. 31, 1993, describes a power steering system for an outboard motor. The system is w mounted upon the body of a hull and includes a steering bracket secured to the body of the hull, a swivel bracket rotatable about a body of the outboard motor, and a pair of clamping brackets supporting the swivel bracket. It comprises a manual steering unit for manually steering a steering element so as to operate the outboard motor. The manual steering unit includes a link mechanism connected to the steering element and connected to the steering bracket. It also comprises a power unit operatively connected to the link mechanism of the manual steering unit.
U.S. Pat. No. 5,244,426, which issued to Miyashita et al on Sep. 14, 1993, describes a power steering system for an outboard motor. The system is disposed outside of rear portion of a hull and usually includes a manual steering system mounted upon the hull for operating a steering element so as to manual steer the outboard motor body. A power unit is operatively connected to the manual steering system and includes an electric motor for applying a steering assist force to the manual steering system.
U.S. Pat. No. 5,626,502, which issued to Novey on May 6, 1997, describes a power steering adapter for outboard powerheads of various size. The adapter is intended to accommodate variations in size and design of outboard motor powerheads, to couple a power steering servo unit to the powerhead, and to utilize existent mounting brackets and steering brackets without restriction on powerhead use. It is characterized by an anchor socket pivoted on a transverse mounting bracket axis to secure a motor operated tiller member at a fixed steering position that shifts its steering center eccentrically with respect to the turning center of the powerhead. The anchor socket accommodates angular displacement caused by the eccentricity.
Various types of bearing materials are available in commercial quantity and are suitable for use within the steering components of a marine propulsion system.
U.S. Pat. No. 3,994,814, which issued to Cairns on Nov. 30, 1976, describes a low friction bearing material and method. The low friction bearing composition comprises a major portion of a thermal plastic resin other than polytetrafluoroethylene and a minor portion of a filled polytetrafluoroethylene material, with the filled polytetrafluoroethylene material consisting essentially of at least 50% by volume of polytetrafluoroethylene polymer and the remainder being a filler material, with the filler material comprising a first filler material and a second, different filler material, the first filler material being selected from the group of soft metals and soft metallic oxides or sulfides having lubricating properties such as lead and its oxides, cadmium and its oxides, titanium oxide, zinc oxide, molybdenum disulfide, and antimony and its oxides and trioxides.
U.S. Pat. No. 3,896,036, which issued to Cairns on Jul. 22, 1975, describes various bearing compositions. The bearing material can comprise, in percent by volume, 40% to 95% of a fluorocarbon resin, such as polytetrafluoroethylene, 5% to 60% of cadmium or an oxide of cadmium, and from 0.1% to about 35% of a filler characterized by a hardness greater than the hardness of cadmium oxide.
U.S. Pat. No. 3,879,301, which issued to Cairns on Apr. 22, 1975, describes a low friction bearing material and method. The bearing composition comprises a major portion of a thermoplastic resin other than polytetrafluoroethylene and a minor portion of a filled polytetrafluoroethylene material, with the filled polytetrafluoroethylene material consisting essentially of at least 50 percent by volume of polytetrafluoroethylene polymer and the remainder being a filler material selected from the group consisting of carbon, glass, asbestos, silica, zinc, cadmium, lead and the oxides thereof, bronze, molybdenum disulfide, tungsten disulfide, alumina, zirconia, titanium oxide, cupric oxide, boron nitride, kieselguhr and mixtures thereof.
U.S. Pat. No. 6,146,220, which issued to Alby et al on Nov. 14, 2000, discloses a pedestal mount for an outboard motor. The outboard motor is mounted to a transom of a boat with a pedestal that is attached either directly to the transom or to an intermediate plate that is, in turn, attached to the transom. A motor support platform is attached to the outboard motor, and a steering mechanism is attached to both pedestal and the motor support platform. The tilting mechanism is attached to the motor support platform and to the outboard motor. The outboard motor is rotatable about a tilting axis relative to both pedestal and the motor support platform. The tilting mechanism is rotatable relative to the pedestal and about a steering axis. The steering axis is generally vertical and stationary relative to the pedestal and is unaffected by the tilting of the outboard motor. The tilting mechanism is rotatable relative to the pedestal and about the steering axis with the outboard motor.
U.S. Pat. No. 6,183,321 B1, which issued to Alby et al on Feb. 6, 2001, discloses an outboard motor with a hydraulic pump and an electric motor located within a steering mechanism. The outboard motor comprises a pedestal that is attached to the transom of a boat, a motor support platform that is attached to the outboard motor, and a steering mechanism that is attached to both the pedestal and the motor support platform. It comprises a hydraulic tilting mechanism that is attached to the motor support platform and to the outboard motor. The outboard motor is rotatable about a tilt axis relative to both the pedestal and the motor support platform. A hydraulic pump is connected in fluid communication with the hydraulic tilting mechanism to provide pressurized fluid to cause the outboard motor to rotate about its tilting axis. An electric motor is connected in torque transmitting relation with the hydraulic pump. Both the electric motor and the hydraulic pump are disposed within the steering mechanism.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Known types of steering devices, such as hydraulic steering and power steering systems, all require that a hydraulic cylinder and piston assembly be mounted in some way to the marine propulsion system, to its bracket, or to the transom of a boat in such a way that tilting the marine propulsion system or rotating the marine propulsion system about its steering axis causes movement of the cylinder relative to the marine vessel or, alternatively, causes relative movement about different axes of rotation between the marine propulsion system and the steering mechanism. It would therefore be significantly beneficial if a hydraulic steering system or power steering system could be provided in which the steering mechanism was an integral portion of the marine propulsion system.
A marine propulsion system made in accordance with the preferred embodiment of the present invention comprises a support structure that is attachable to both a marine propulsion system and to a marine vessel. The marine propulsion system is rotatable about a generally vertical steering axis and also about a generally horizontal tilting axis. A steering arm is attachable to the marine propulsion system and is rotatable about the steering axis. A steering actuator has a first portion attached to the support structure and a second portion attached in force transmitting relation with the steering arm. The first portion remains stationary with respect to the support structure during rotation of the marine propulsion system about either the steering axis or the tilting axis.
In a preferred embodiment of the present invention, the second portion of the steering actuator is moveable along a generally straight line relative to the first portion of the steering actuator. A sliding joint is attached to the second portion of the steering actuator and comprises a linear component and a rotational component. The linear component is attached to the second portion of the steering actuator and the rotational component is disposed within the linear component and rotatable relative to the linear component. The rotational component is shaped to receive the steering arm in sliding relation therein.
The marine propulsion system of the present invention can be either an outboard motor or a stem drive system. The steering actuator, in a preferred embodiment of the present invention, is a hydraulic actuator with the first portion of the steering actuator comprising a hydraulic cylinder and the second portion of the steering actuator comprising a moveable piston within the cylinder in response to changes in hydraulic pressure within the cylinder.